1. Field of the Invention
The present invention relates to a picture information converting apparatus and a picture information converting method.
2. Description of the Related Art
In high audio-visual environments, television receivers that can display pictures with high resolution have been desired. To satisfy that, a so-called high-vision (high definition television) system has been developed. In the high-vision system, the number of scanning lines is 1125 that is more than twice of that of the conventional NTSC system. In the high-vision system, the aspect ratioxe2x80x94the ratio of the frame width to the frame height is 9:16 that is wider than 3:4 of the NTSC system. Thus, in the high-vision system, pictures that have high resolution and presence can be obtained.
When an NTSC format picture signal is supplied to a high-vision receiver, it cannot display a picture due to the difference of the signal format. To solve such a problem, with a picture information converting apparatus as shown in FIG. 1, the rate of the picture signal is converted. Referring to FIG. 1, an NTSC format picture signal as an SD (Standard Definition) signal is input from an input terminal 100 to a horizontal interpolation filter 101. The horizontal interpolation filter 101 performs a horizontal interpolation process for the NTSC format picture signal. The output signal of the horizontal interpolation filter 101 is supplied to a vertical interpolation filter 102. The vertical interpolation filter 102 performs a vertical interpolation process for the output signal of the horizontal interpolation filter 101. The vertical interpolation filter 102 outputs a high-vision format picture signal as an HD (High Definition) signal.
Next, with reference to FIG. 2, a practical structure of the horizontal interpolation filter 101 will be described., Referring to FIG. 2, an NTSC format picture signal is supplied from an input terminal 100 to (m+1) multiplying devices 111m, 111mxe2x88x921, 111mxe2x88x922, . . . , and 1110. The multiplying devices 111m, 111mxe2x88x921, 111mxe2x88x922, . . . , and 1110 multiply the received signal by respective coefficients and supply the calculated results to adding devices 112mxe2x88x921, 112mxe2x88x922, . . . , and 1120, respectively. Output signals of the adding devices 112mxe2x88x921, 112mxe2x88x922, . . . , and 1120 are supplied to delay. registers 113mxe2x88x921, 113mxe2x88x922, . . . , and 1130, respectively. Output signals of the delay registers 113mxe2x88x921, 113mxe2x88x922, . . . , and 1130, are supplied to adding devices 112mxe2x88x922, 112mxe2x88x923, . . . , and 1120, respectively.
An output signal of the multiplying device 111m is supplied to a delay register 113m. An output signal of a delay register 113m is supplied to the adding device 112mxe2x88x921. The delay registers 113mxe2x88x921, 113mxe2x88x922, . . . , and 1130 delay their received signals by a delay time period T.
Thus, the NTSC format picture signal that is received through the input terminal 100 is supplied to the delay register 113m. The delay register 113m delays the NTSC format picture signal by a time period T. The resultant picture signal is supplied to the adding device 112mxe2x88x921. The adding device 112mxe2x88x921 adds the output signal of the delay register 113m and the output signal of the multiplying device 113mxe2x88x921 and supplies the resultant signal to the delaying device 113mxe2x88x921. The delay register 113mxe2x88x921 delays the output signal of the adding device 112mxe2x88x921 by the time period T and supplies the resultant signal to the adding device 112mxe2x88x922. The adding device 112mxe2x88x922 adds the output signal of the delay register 113mxe2x88x922 and the output signal of the multiplying device 111mxe2x88x922 and supplies the resultant signal to the next delaying device.
Next, the similar process is repeatedly performed. The adding device 1120 on the last stage adds the output signal of the delay register 1130 and the output signal of the multiplying device 1110 and supplies the resultant signal as the final output signal of the horizontal interpolation filter 101 (namely, the output picture signal of the horizontal interpolation process) to the vertical interpolation filter 102 through an output terminal 120.
The structure of the vertical interpolation filter 102 is similar to that of the horizontal interpolation filter 101. The vertical interpolation filter 101 performs a vertical interpolation process for the output signal of the horizontal interpolation filter 101 and supplies the resultant signal as a high-vision format picture signal to a high-vision receiver. In such a picture information converting process, an NTSC format picture signal can be displayed on a high-vision receiver.
In the above-described picture information converting process, an NTSC format picture signal is simply interpolated in the horizontal direction and the vertical direction. Thus, the resolution of the converted picture signal is the same as that of the original picture signal. In particular, when a normal moving picture is converted, the vertical interpolation process is performed as an intra-field process. In such a process, since the inter-field correlation of the picture is not used, due to a conversion loss, the resolution of the converted picture signal may deteriorate against that of the original picture signal.
To solve such a problem, the applicant of the present invention has proposed an apparatus that performs a class categorization adaptive process as a picture information converting process (see Japanese Patent Laid-Open Publication No. 6-205934). In the class categorization adaptive process, an input SD signal is categorized as a class corresponding to a three-dimensional (time-space) distribution of the signal level. Predictive coefficients pre-learnt for individual classes are stored in a memory. With the results of the class categorization and the predictive coefficients, a calculation corresponding to a predetermined predictive expression is performed so as to generate an optimum estimated value as an HD pixel.
In the class categorization adaptive process, with SD pixel data present in the vicinity of an HD pixel to be generated, the class categorization process is performed. Predictive coefficients are pre-leant for individual classes detected in the class categorization process. For a still picture portion, using the intra-frame correlation, an HD pixel value closer to a real value is obtained. For a moving picture portion, using the inter-field correlation, an HD pixel value closer to a real value is obtained.
Next, a real example of such a process for generating HD pixels y1 and y2 shown in FIG. 3 will be described. The averages of frame differences of pixels present at the spatially same position are obtained for SD pixels m1 to m5 and SD pixels n1 to n5. The obtained values are categorized as motion classes using predetermined threshold values. In addition, SD pixels k1 to k5 shown in FIG. 4 are processed by ADRC (Adaptive Dynamic Range Coding) method. Thus, with a small number of bits, a class categorization that represents a spatial waveform can be performed.
For each class determined by the above-described two types of class categorizations, HD pixels y1 and y2 are generated by a calculation corresponding to the following linear expression (1).
y=w1xc3x97x1+w2xc3x97x2+ . . . +wnxc3x97xnxe2x80x83xe2x80x83(1)
FIG. 5 shows an example of the arrangement of SD pixels x1, x2, . . . , and xn used in such a calculation. In this example, 17 SD pixels (n=17) are used. The predictive coefficients w1 to wn used in formula (1) are pre-learnt. In such a process, since the class categorization that represents the amount of a motion and the class categorization that represents a spatial waveform are independently and adaptively preformed, a high conversion capability can be accomplished with a relatively small number of classes.
In such a class categorization adaptive process, an interlace signal with scanning lines twice as many as that of an input interlace signal can be obtained. For example, a 525i signal as an input picture signal can be converted into a 1050i signal as an output. picture signal. Thus, the picture becomes dense and thereby the picture quality thereof improves.
In the class categorization adaptive process, an input interlace signal can be converted into a progressive signal with the same number of scanning lines. For example, a 525i signal as an input picture signal can be converted into a 525p signal as an output picture signal. Thus, as an effect of the converting process, line flicker can be removed.
Although such two types of conversions have respective effects, if they are accomplished with one apparatus, memories that store predictive coefficients for these conversions are required. Thus, the circuit scale of the apparatus becomes large.
The present invention is made from the above-described point of view. An object of the present invention is to provide a picture information converting apparatus and a picture information converting method that allow an input picture signal to be converted into two or more types of output picture signals without need to increase the circuit scale of the apparatus or with a minimum increase thereof. A first aspect of the present invention is a picture information converting apparatus for generating an output picture signal with a scanning line structure different from an input picture signal, comprising a field-by-field vertical inverting means for selectively performing a vertical inverting process for the input picture signal for each field corresponding to the type of the input picture signal and the type of the output picture signal, a first picture extracting means for extracting picture data at a predetermined position of the input picture signal, a motion class detecting means for determining a motion class that represents a motion with the picture data extracted by the first picture extracting means and outputting information corresponding to the determined motion class, a second picture extracting:means for extracting picture data at a predetermined position from the input picture signal, a spatial class detecting means for detecting a pattern of a level distribution of picture data extracted by the second picture extracting means, determining a spatial class of the picture data corresponding to the detected pattern, and outputting information that represents the spatial class, a class code generating means for combining an output signal of the motion class detecting means and an output signal of the spatial class detecting means, a storing means for storing predetermined coefficient data predetermined corresponding to an output signal of the class code generating means, a third picture extracting means for extracting picture data at a predetermined position from the input picture signal, and a calculation process means for performing a calculation for estimating an output picture signal corresponding to an output signal of the class code generating means with predictive coefficient data selected by the storing means and picture data selected by the third picture data selecting means.
A second aspect of the present invention is a picture information converting method for generating an output picture signal with a scanning line structure different from an input picture signal, comprising the steps of (a) selectively performing a vertical inverting process for the input picture signal for each field corresponding to the type of the input picture signal and the type of the output picture signal, (b) extracting picture data at a predetermined position of the input picture signal, (c) determining a motion class that represents a motion with the picture data extracted at step (b) and outputting information corresponding to the determined motion class, (d) extracting picture data at a predetermined position from the input picture signal, (e) detecting a pattern of a level distribution of picture data extracted at step (d), determining a spatial class of the picture data corresponding to the detected pattern, and outputting information that represents the spatial class, (f) combining an output signal of step (c) and an output signal of step (e), (g) storing predetermined coefficient data predetermined corresponding to an output signal of step (f), (h) extracting picture data at a predetermined position from the input picture signal, and (i) performing a calculation for estimating an output picture signal corresponding to an output signal of step (f) with predictive coefficient data selected at step (g) and picture data selected at step (h).
According to the present invention, corresponding to the type of an input picture signal and the type of an output picture signal, field-by-field vertical inverting process is selectively performed. For the resultant signal, the picture information converting process is performed.
As described above, according to the present invention, before the picture information converting process is performed, the SD picture signal inverting process is selectively performed. Thus, with the same coefficient data, two or more types of HD picture signals can be generated.
Thus, it is not necessary to store different types of coefficient data for generating two or more types of HD picture signals. Consequently, when two or more types of HD picture signals are generated, it is not necessary to increase the storage capacity of the memory for storing the coefficient data. Thus, the circuit scale of the memory can be prevented from increasing.
Thus, an apparatus that has a function for generating two or more types of HD picture signals can be accomplished without need to increase the circuit scale and cost or with a minimum increase thereof.
As prior art references of the present invention, the following patent applications were filed by the applicant of the present invention and the following USP was granted thereto.
(1) Japanese Patent Application No. H09-115437 (U.S. patent application corresponding thereto is now pending),
(2) Japanese Patent Application No. H10-228221 (U.S. patent application corresponding thereto is now pending), and
(3) U.S. Pat. No. 5,049,990
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.